The invention described herein is related to the field of vehicle guidance of multiple vehicles participating in common, coordinated maneuvers. More specifically, the present invention relates to a method for conducting a vehicle within constraints of a coordinated maneuver by providing state data of other vehicles participating in the maneuver through broadcast means and predicting the states of the vehicles for future times of the coordinated maneuver given the constraints thereof.
The problem of coordinating multiple vehicles in a common maneuver is beset with complications of communication and control. These problems are compounded as the number of vehicles participating in the maneuver increases and by the complexity of the maneuver itself. Indeed, for extremely complex maneuvers, such as the ballet of multiple aircraft in precision military flight maneuvers, reliance is placed primarily on the aircraft pilot to make instantaneous decisions as automated control of the aircraft during such maneuvers is impractical.
For classes of simpler maneuvers, numerous systems and methods for coordinating vehicles within the maneuver have been investigated and implemented. One such system is disclosed in U.S. Pat. No. 6,271,768 to Fraser, Jr., et al., which provides a display for a dual mode Traffic Collision Avoidance System (TCAS)/Intra-Formation Position Collision Avoidance System (IFPCAS) and requires the cooperation of at least two formation follower aircraft in conjunction with a formation lead aircraft. The TCAS receives and processes broadcast data from another data link transponder that is located onboard another aircraft (e.g., a follower aircraft within a formation cell) to determine relative aircraft position of the host aircraft with respect to the other aircraft. The system includes a high-speed digital communication link that is operatively connected to a mission computer used to transmit steering commands to a transponder-equipped follower aircraft. The follower aircraft uses the steering commands to position itself with respect to the formation lead vehicle. Thus, each follower aircraft simply mimics commands from the formation lead aircraft to participate in the maneuver. Thus, if the lead aircraft were in some way disabled, the follower aircraft would no longer be able to participate in the maneuver via the established coordination mechanism.
Another simple coordinated maneuver which may benefit from coordination mechanisms is that of final approach spacing of aircraft at the runway of an airport. At busy terminal runways, it is imperative to land as many aircraft as can be safely achieved. During instrument flight conditions, significant constraints are placed on aircraft longitudinal separation on final approach. Aircraft spacing during such instrument flight conditions is primarily controlled by ground based air traffic controller judgment. At present, there are no significant aids available to assist the controller in optimizing spacing. During visual flight conditions, pilots are asked to adequately space themselves behind the aircraft in front of them. The pilot is asked to rely primarily on his own judgment through visual means. During both visual and instrument flight conditions, the lack of maneuver coordination automation tools to assist either the pilot or the controller results in an unnecessary under-utilization of potential runway capacity.
An object of the present invention is to provide a method for conducting a moving vehicle along a trajectory of a coordinated maneuver by: a) receiving state information from other vehicles participating in the maneuver over a broadcast communication link; b) using the state data of the other vehicles and the state data of the moving vehicle to predict the states of the participating vehicles at future times for which the maneuver is to be conducted; and, c) adjusting the state of the moving vehicle so that a predicted coordinated maneuver based on the adjusted state of the moving vehicle and the states of the other vehicles indicates a successful completion of the maneuver.
In one embodiment of the present invention, a projected coordinated maneuver is determined by forward time integration so as to predict the states of all participating vehicles at any given time from a current time to a future time in which the coordinated maneuver is predicted to complete, given the individual vehicle states at the current time as initial conditions and governed by constraints of control parameters known to all participating vehicles. This is generally accomplished by calculating the projected maneuver for the moving vehicle, designated as an own-vehicle, based on the own-vehicle state and forwardly integrating the state of the own-vehicle with respect to time, given the projected trajectories of the other vehicles participating in the maneuver to determine if the maneuver can be completed in compliance with the constraints of the control parameters. The projected maneuvers of the other vehicles are transmitted over broadcast links or may be calculated onboard the own-vehicle from the state data of the other vehicles provided thereto.
In a preferred embodiment of the present invention, the method is applied to controlling aircraft spacing on final approach to the runway of an airport and is controlled in the cockpit of the aircraft rather than dictated by ground-based controllers. The algorithm of the present invention produces a planned speed profile for the own-vehicle given known deceleration points and target air speeds at those deceleration points. State information from an aircraft preceding the own-vehicle in landing order, designated the lead-vehicle, is communicated to the own-vehicle via Automatic Dependent Surveillance Broadcasts (ADS-B), or via point-to-point data link communications. The algorithm revises the own-vehicle""s speed profile, if necessary, to avoid potential or predicted violation of an applicable vehicle separation standard.
In a preferred embodiment, the speed profile of the participating vehicles is characterized by constant speed intervals between planned deceleration points. This allows the flight crew of the participating vehicles the freedom to perform other duties required for a safe landing without the need for continual speed adjustments. The algorithm further allows for fuel efficient flight profiles while simultaneously solving the optimal spacing problem. Moreover, the algorithm allows for higher runway throughput as compared with prior art final approach maneuvers.